This poll is shocking! Makeup brushes can harbor bacteria and dirt which are transferred onto the skin and eyes when you use them.
Makeup brushes that you use everyday should be cleaned every 3-4 weeks.
Rinse your brushes in lukewarm water to remove residual makeup. Focus on the actual bristles and avoid the base of the brush as much as possible since this can weaken the glue over time.
Squirt a small amount of your facial cleanser in the palm of your hand and gently swirl the brush tip in the cleanser to work up a lather.
Rinse the brush tip under running water.
Lay your brushes flat on a cloth to dry, reshape the bristles as necessary.
I wash my brushes in the morning after I’ve used them so they will be dry by the following morning. If they are still damp, a quick pass with the hair dryer does the trick!